1. Field of the Invention
This invention relates to a process for prolonging the shelf life of fresh vegetables. More particularly, it relates to prolonging the shelf life of vegetables having enlarged petioles. This invention especially relates to prolonging the shelf life of celery.
2. Description of the Prior Art
Fresh fruits and vegetables are extremely perishable commodities. Heretofore, many techniques have been employed to protect such food products from oxidative degradation, mold attack and moisture penetration and to preserve the freshness, texture and color of the fresh produce. One of the earliest means of lengthening the shelf life of fruits and vegetables was refrigeration. However, most fresh produce, when stored under reduced temperatures for prolonged periods, shows adverse effects on the taste, odor or quality of the product which is caused by biochemical changes and microbial growth. In addition, storage temperatures below 35.degree. F. often cause chill injury to the tissue of the produce. Hence, in many instances, refrigeration alone is not effective in achieving the desired shelf life for a particular fruit or vegetable.
Coating fresh fruits and/or vegetables is another of these techniques which has been employed with varying degrees of success. Not only must the coating be effective in prolonging the useful shelf life of fresh produce, but the appearance of the commodity must not be altered from that of its natural state. At a minimum, this natural appearance must not only remain unchanged but should ideally be enhanced especially when the fruit or vegetable will be displayed for sale. The selection of a coating material is further indicated where the fruit or vegetable is to be consumed in its natural state, and it is considered essential that there be no need to remove the coating. In that event, the coating material must not only be edible, it should not affect or alter the natural organoleptic characteristics of the fresh fruit or vegetable.
Typical of these prior art coatings are the wax emulsions of U.S. Pat. No. 2,560,820 to Recker and U.S. Pat. No. 2,703,760 to Cunning. Coatings of natural materials have been employed including milk whey (U.S. Pat. No. 2,282,801 to Musher), lecithin (U.S. Pat. No. 2,470,281 to Allingham and U.S. Pat. No. 3,451,826 to Mulder), gelatin together with polyhydric alcohol (U.S. Patent to Whitman, et al.) and protein (U.S. Pat. No. 4,344,971 to Garbutt). Polymers have also been used extensively, viz., a thermoplastic polymer (U.S. Pat. No. 2,213,577 to Tisdale, et al.), vinyl acetate polymer (U.S. Pat. No. 3,410,696 to Rosenfield), a hydrophilic polymer (U.S. Pat. No. 3,669,691 to De Long, et al.) and the combination of a water soluble polymer and hydrophobic material (U.S. Pat. No. 3,997,674 to Ukai, et al.). Cellulosic materials have found utility in coating fruits and vegetables including hydrated cellulose (U.S. Pat. No. 1,774,866 to Beadle), a combination of cellulose and wax (U.S. Pat. No. 2,364,614 to Beatty), cellulose ether in combination with a fatty acid ester (U.S. Pat. No. 3,471,303 to Hamdy, et al.) or monoglyceride and a fatty acid metal salt (U.S. Pat. No. 3,461,304 to Hamdy, et al.), or a sucrose ester of a fatty acid (U.S. Pat. No. 4,338,342 to Tan, et al.).
Food preservation has for many years employed such mutually exclusive processes as dehydration and freezing. Both of these operations often include a heat treatment, known as blanching, which is conducted prior to the dehydration or freezing step. Blanching is said to reduce enzyme or bacteria level and to prevent or minimize undesirable changes during storage in the dry or frozen state, such as changes in color, odor, texture or loss of vitamins.
The cutting of fresh fruits and vegetables is generally disclosed in the prior art by several references. For instance, U.S. Pat. No. 4,157,681 to Ahesson, et al. describe the use of a machine for paring fruits and vegetables. Further, U.S. Pat. Nos. 2,475,142 to Kane and 2,437,637 to Bridge describe similar type machines for paring and slicing different fruits and vegetables.
While the art has provided several methods to extend the shelf life of vegetables or fruits, the need still exists for methods of extending the shelf life of fruits or vegetables that are more effective than previous methods have been able to accomplish.
Accordingly, it is one object of the present invention to prolong the post harvest life of fresh vegetables having enlarged petioles as a predominant feature.
Another object of the present invention is to prolong the shelf life of fresh celery.
A further object of this invention is to provide raw celery in a ready-to-eat form and to improve the shelf life of this fresh celery.
The achievement of these and other objects will be apparent from the following description of the subject invention.